Arthritis doens’t just affect older Americans, a new study says young people have arthritis in higher numbers than previously thought.

Younger Americans are suffering from the pains of arthritis in higher numbers, according to new research in the journal Arthritis and Rheumatology.

Previous studies in national arthritis estimates was based on a single survey question — whether a doctor ever told them they have arthritis — which misses many factors. The new study, from Boston University School of Medicine, based their survey on three factors: doctor diagnosis, chronic joint symptoms, and duration of symptoms for longer than three months.

The researchers surveyed over 33,000 participants and found that more young people had the joint pain and inflammation that marks the chronic condition.

As of 2015, the year of the study, one-third of Americans ages 18-65 reported doctor diagnosis arthritis — about 30% percent of men and more than 31% of women.

An additional 19% of men and nearly 17% of women reported joint symptoms or pain. For adults 65 and older, more than 55% were men and about 69% were women.

The Arthritis Foundation states about 50 million adults, a quarter of Americans, have doctor-diagnosed arthritis. But the Boston University research ups that number to more than 91 million, just over a third of the adult population.

"Our findings are important because of underestimated, yet enormous, economic and public health impacts of arthritis including healthcare costs and costs from loss of productivity and disability, including in adults younger than 65 years of age," said S. Reza Jafarzadeh, one of the co-authors of the research in a statement.

Doctors often miss arthritis diagnoses in patients under 65 because they don’t expect to see it, the researchers said.

The Arthritis Foundation says there is no sure way to prevent arthritis, but you can reduce your risk and delay onset depending on the type of arthritis. Maintaining a healthy weight, not smoking, avoiding sports injuries and a healthy diet are ways to prevent or delay types of arthritis like osteoarthritis, rheumatoid arthritis and gout.